The shedding of severe acute respiratory syndrome coronavirus (SARS-CoV) into saliva droplets plays a critical role in viral transmission. The source of high viral loads in saliva, however, remains elusive. Here we investigate the early target cells of infection in the entire array of respiratory tissues in Chinese macaques after intranasal inoculations with a single-cycle pseudotyped virus and a pathogenic SARS-CoV. We found that angiotensin-converting enzyme 2-positive (ACE2⁺) cells were widely distributed in the upper respiratory tract, and ACE2⁺epithelial cells lining salivary gland ducts were the early target cells productively infected. Our findings also have implications for SARS-CoV early diagnosis and prevention.

Objective: Myeloid-derived suppressor cells (MDSCs) contribute to tumour immunosuppressive microenvironment and immune-checkpoint blockade resistance. Emerging evidence highlights the pivotal functions of cyclin-dependent kinases (CDKs) in tumour immunity. Here we elucidated the role of tumour-intrinsic CDK20, or cell cycle-related kinase (CCRK) on immunosuppression in hepatocellular carcinoma (HCC). Design: Immunosuppression of MDSCs derived from patients with HCC and relationship with CCRK were determined by flow cytometry, expression analyses and co-culture systems. Mechanistic studies were also conducted in liver-specific CCRK -inducible transgenic (TG) mice and Hepa1–6 orthotopic HCC models using CRISPR/Cas9-mediated Ccrk depletion and liver-targeted nanoparticles for interleukin (IL) 6 trapping. Tumorigenicity and immunophenotype were assessed on single or combined antiprogrammed death-1-ligand 1 (PD-L1) therapy. Results: Tumour-infiltrating CD11b ⁺ CD33 ⁺ HLA-DR ⁻ MDSCs from patients with HCC potently inhibited autologous CD8 ⁺ T cell proliferation. Concordant overexpression of CCRK and MDSC markers (CD11b/CD33) positively correlated with poorer survival rates. Hepatocellular CCRK stimulated immunosuppressive CD11b ⁺ CD33 ⁺ HLA-DR ⁻ MDSC expansion from human peripheral blood mononuclear cells through upregulating IL-6. Mechanistically, CCRK activated nuclear factor-κB (NF-κB) via enhancer of zeste homolog 2 (EZH2) and facilitated NF-κB-EZH2 co-binding to IL-6 promoter. Hepatic CCRK induction in TG mice activated the EZH2/NF-κB/IL-6 cascade, leading to accumulation of polymorphonuclear (PMN) MDSCs with potent T cell suppressive activity. In contrast, inhibiting tumorous Ccrk or hepatic IL-6 increased interferon γ ⁺ tumour necrosis factor-α ⁺ CD8 ⁺ T cell infiltration and impaired tumorigenicity, which was rescued by restoring PMN-MDSCs. Notably, tumorous Ccrk depletion upregulated PD-L1 expression and increased intratumorous CD8 ⁺ T cells, thus enhancing PD-L1 blockade efficacy to eradicate HCC. Conclusion: Our results delineate an immunosuppressive mechanism of the hepatoma-intrinsic CCRK signalling and highlight an overexpressed kinase target whose inhibition might empower HCC immunotherapy.

Insufficient T cell infiltration into noninflamed tumors, such as hepatocellular carcinoma (HCC), restricts the effectiveness of immune-checkpoint blockade (ICB) for a subset of patients. Epigenetic therapy provides further opportunities to rewire cancer-associated transcriptional programs, but whether and how selective epigenetic inhibition counteracts the immune-excluded phenotype remain incompletely defined. Here, we showed that pharmacological inhibition of histone deacetylase 8 (HDAC8), a histone H3 lysine 27 (H3K27)–specific isozyme overexpressed in a variety of human cancers, thwarts HCC tumorigenicity in a T cell–dependent manner. The tumor-suppressive effect of selective HDAC8 inhibition was abrogated by CD8⁺ T cell depletion or regulatory T cell adoptive transfer. Chromatin profiling of human HDAC8-expressing HCCs revealed genome-wide H3K27 deacetylation in 1251 silenced enhancer-target gene pairs that are enriched in metabolic and immune regulators. Mechanistically, down-regulation of HDAC8 increased global and enhancer acetylation of H3K27 to reactivate production of T cell–trafficking chemokines by HCC cells, thus relieving T cell exclusion in both immunodeficient and humanized mouse models. In an HCC preclinical model, selective HDAC8 inhibition increased tumor-infiltrating CD8⁺ T cells and potentiated eradication of established hepatomas by anti–PD-L1 therapy without evidence of toxicity. Mice treated with HDAC8 and PD-L1 coblockade were protected against subsequent tumor rechallenge as a result of the induction of memory T cells and remained tumor-free for greater than 15 months. Collectively, our study demonstrates that selective HDAC8 inhibition elicits effective and durable responses to ICB by co-opting adaptive immunity through enhancer reprogramming.

Colorectal cancer (CRC) patients with mismatch repair (MMR)-deficient (dMMR) but not MMR-proficient (pMMR) tend to benefit from immune checkpoint blockade (ICB) therapy. To profile the tumor microenvironments (TME) underlying these varied therapeutic responses, we integrate spatial enhanced resolution omics-sequencing (Stereo-seq), single-cell RNA sequencing, and multiplexed imaging analysis to create high-definition spatial maps of tumors from treatment-naïve and ICB-treated CRC patients. Our results identify the spatial organization and immune status of the tumor-stroma boundary as a distinctive feature of dMMR and pMMR CRCs, which associates with ICB response. The physical interactions and abundance of LAMP3⁺DCs and CXCL13⁺T cells may shape the ICB-responsive tumor-stroma boundary, whereas CXCL14⁺cancer-associated fibroblasts tend to remodel extracellular matrix to form a structural barrier in non-responders. Our work therefore points out the importance of the molecular and cellular spatial structures of tumors in ICB response, raising the possibility of reprogramming tumor-stroma boundary for sensitizing immunotherapies in the majority of CRCs.

Obesity increases the risk of hepatocellular carcinoma (HCC) especially in men, but the molecular mechanism remains obscure. Here, we show that an androgen receptor (AR)-driven oncogene, cell cycle-related kinase (CCRK), collaborates with obesity-induced pro-inflammatory signaling to promote non-alcoholic steatohepatitis (NASH)-related hepatocarcinogenesis. Lentivirus-mediatedCcrkablation in liver of male mice fed with high-fat high-carbohydrate diet abrogates not only obesity-associated lipid accumulation, glucose intolerance and insulin resistance, but also HCC development. Mechanistically, CCRK fuels a feedforward loop by inducing STAT3-AR promoter co-occupancy and transcriptional up-regulation, which in turn activates mTORC1/4E-BP1/S6K/SREBP1 cascades via GSK3β phosphorylation. Moreover, hepaticCCRKinduction in transgenic mice stimulates mTORC1-dependentG⁻csfexpression to enhance polymorphonuclear myeloid-derived suppressor cell recruitment and tumorigenicity. Finally, the STAT3-AR-CCRK-mTORC1 pathway components are concordantly over-expressed in human NASH-associated HCCs. These findings unveil the dual roles of an inflammatory-CCRK circuitry in driving metabolic and immunosuppressive reprogramming through mTORC1 activation, thereby establishing a pro-tumorigenic microenvironment for HCC development.